The Sctruct
I am not much of a C# or C programmer and have not found much guidance on specifying pointers and structs within a struct. I am attempting to import the following from a C dll into a C# program:
#define MAXFILENAME 259
struct IDentry {
char* IDname;
int length;
};
typedef struct IDentry idEntry;
struct SMOutputAPI {
char name[MAXFILENAME + 1];
FILE* file;
struct IDentry *elementNames;
long Nperiods;
int FlowUnits;
int Nsubcatch;
int Nnodes;
int Nlinks;
int Npolluts;
int SubcatchVars;
int NodeVars;
int LinkVars;
int SysVars;
double StartDate;
int ReportStep;
__int64 IDPos;
__int64 ObjPropPos;
__int64 ResultsPos;
__int64 BytesPerPeriod;
};
I am not sure how to handle the *elementsNames, file or name properties. What I have so far in C# is:
int MAXFILENAME = 259
[StructLayout(LayoutKind.Sequential)]
public struct SMOutputAPI
{
[MarshalAs(UnmanagedType.ByValArray, SizeConst = MAXFILENAME+1)]
public string name;
IntPtr file;
IntPtr elementNames;
public long Nperiods;
public int FlowUnits;
public int Nsubcatch;
public int Nnodes;
public int Nlinks;
public int Npolluts;
public int SubcatchVars;
public int NodeVars;
public int LinkVars;
public int SysVars;
public double StartDate;
public int ReportStep;
public int IDPos;
public int ObjPropPos;
public int ResultsPos;
public int BytesPerPeriod;
};
The C# application builds fine, but when I call the C initialization function that should return a new SMOutputAPI struct I get an error:
System.Runtime.InteropServices.MarshalDirectiveException
Method's type signature is not PInvoke compatible.
Any thoughts on how to properly specify this struct in C# would be much appreciated. Thanks!
Initializing the Struct
The struct is initialized in the c-code with:
SMOutputAPI* DLLEXPORT SMO_init(void)
//
// Purpose: Returns an initialized pointer for the opaque SMOutputAPI
// structure.
//
{
SMOutputAPI *smoapi = malloc(sizeof(struct SMOutputAPI));
smoapi->elementNames = NULL;
return smoapi;
}
The corresponding c# code is:
[DllImport("swmm-output.dll")]
static extern SMOutputAPI SMO_init();
static void Main(string[] args)
{
Console.Write("Hello World!");
SMOutputAPI SMO = SMO_init();
}
Related
How would you marshall this nested array of structure in C#?
C struct:
typedef struct
{
unsigned int appVersionNumber;
unsigned int networkId;
struct
{
int code;
int endDate;
} profiles[4];
} CardEnvHolder;
My C# attempt:
[StructLayout(LayoutKind.Sequential)]
unsafe struct CardEnvHolder
{
public uint appVersionNumber;
public uint networkId;
public Profiles[] profiles;
}
[StructLayout(LayoutKind.Sequential)]
struct Profiles
{
public int code;
public int endDate;
}
C# Main:
unsafe
{
CardEnvHolder envhold = new CardEnvHolder();
void* ptr = (void*)&envhold; //Error here
EnvHolderTest(ptr);
Console.WriteLine(envhold.profil[1].code);
}
Unfortunately I get the error CS0208 "Cannot take the address of, get the size of, or declare a pointer to a managed type ('T')"
As requested,
EnvHolder C function:
void EnvHoldInit(CardEnvHolder* envhold)
{
envhold->appVersionNumber = 4;
envhold->networkId = 8;
envhold->profiles[1].code = 84;
printf("%d\n", envhold->profiles[1].code);
envhold->profiles[1].code++;
}
EXPORT void EnvHolderTest(void* envhold)
{
EnvHoldInit(envhold);
}
EnvHolder C# prototype:
[DllImport("Sandbox.dll", CallingConvention = CallingConvention.Cdecl)]
extern static unsafe void EnvHolderTest([In, Out] void* envhold);
I have a simple C++ win32 DLL developed in visual studio 2017 and compiled in 64 bit environment having the following code:
typedef struct sum {
struct {
int num1;
int num2;
} nums;
} sum1;
extern "C" {
__declspec(dllexport) int initialize(sum1 *summing)
{
int res;
res = summing->nums.num1 + summing->nums.num2;
return res;
}
}
The above code contains a method which returns the sum of two integers by taking a typedef struct as an argument.
I have a C# client application which consumes this Win32 C++ DLL using PInvoke. Following is the code of my C# client application:
[StructLayout(LayoutKind.Sequential)]
public struct nums
{
public int a;
public int b;
}
[StructLayout(LayoutKind.Sequential)]
public struct mydef
{
public IntPtr sum;
}
public class LibWrap
{
[DllImport("C++.dll", EntryPoint = "initialize")]
public static extern int Initialize(ref mydef mydef);
}
class Program
{
static void Main(string[] args)
{
mydef mydef = new mydef();
nums nums;
nums.a = 6;
nums.b = 6;
IntPtr buffer1 = Marshal.AllocCoTaskMem(Marshal.SizeOf(nums));
Marshal.StructureToPtr(nums, buffer1, false);
mydef.sum = buffer1;
int res = LibWrap.Initialize(ref mydef);
Console.WriteLine(res);
}
}
With the above code, I am expecting '12' as output, but instead I am getting '-1504178328' as output.
I am a C# developer with no experience in C++ at all. Please help me to solve this problem.
Use a simpler P/Invoke wrapper:
public static class LibWrap
{
[DllImport("C++.dll", EntryPoint = "initialize")]
public static extern int Initialize(ref Nums nums);
[StructLayout(LayoutKind.Sequential)]
public struct Nums
{
public int a;
public int b;
}
}
and use it like this:
void CSharpExample()
{
LibWrap.Nums nums;
nums.a = 6;
nums.b = 7;
int res = LibWrap.Initialize(ref nums);
Console.WriteLine(res);
}
In your example, you don't need any memory allocation and marshaling, because:
LibWrap.Nums is a struct, thus local variable nums in CSharpExample() is allocated completely on stack.
passing managed struct LibWrap.Nums by ref to LibWrap.Initialize will pass the pointer to local variable nums on stack.
LibWrap.Initialize is called synchronously, so that the pointer you pass to it isn't used anywhere after LibWrap.Initialize function exits. This is important because the pointer becomes invalid as soon as CSharpExample() exits.
On the C# side, you are not handling the nested struct correctly. Try this instead:
[StructLayout(LayoutKind.Sequential)]
public struct mynums {
public int num1;
public int num2;
}
[StructLayout(LayoutKind.Sequential)]
public struct sum1 {
public mynums nums;
}
public class LibWrap {
[DllImport("C++.dll", EntryPoint = "initialize")]
public static extern int Initialize(ref sum1 summing);
}
class Program {
static void Main(string[] args) {
sum1 mysum;
mysum.nums.num1 = 6;
mysum.nums.num2 = 6;
int res = LibWrap.Initialize(ref mysum);
Console.WriteLine(res);
}
}
That being said, having a struct whose sole data member is another struct is redundant and unnecessary. You should remove the outer struct altogether, eg:
struct nums {
int num1;
int num2;
};
extern "C" {
__declspec(dllexport) int initialize(nums *summing) {
return summing->num1 + summing->num2;
}
}
[StructLayout(LayoutKind.Sequential)]
public struct nums {
public int num1;
public int num2;
}
public class LibWrap {
[DllImport("C++.dll", EntryPoint = "initialize")]
public static extern int Initialize(ref nums summing);
}
class Program {
static void Main(string[] args) {
nums mynums;
mynums.num1 = 6;
mynums.num2 = 6;
int res = LibWrap.Initialize(ref mynums);
Console.WriteLine(res);
}
}
I have an DLL file named WD_SDK.dll (it go with an SDK.h file).
I open the SDK.h and I see:
typedef void (CALLBACK * VideoCaptureCB_Ptr)(PVOID pContext, BYTE * apData[3],
VideoSampleInfo_T * pVSI);
typedef struct _VideoSampleInfo_T
{
ULONG idFormat; //
ULONG lSignalState;
int nLen; // not used for raw video data(e.g. YUV420)
int nWidth;
int nHeight;
int anPitchs[3]; // only used for raw video data(e.g. YUV420)
ULONG dwMicrosecsPerFrame; // 1000*1000/FPS
ULONG field;
int iSerial;
} VideoSampleInfo_T;
WD_RegisterVideoPreviewCB(HANDLE hChannel, PVOID pContext, VideoCaptureCB_Ptr pCB);
I want to call the WD_RegisterVideoPreviewCB in C#. So I use the DllImport to declare it in C#. It look like this:
[DllImport("WD_SDK.dll", EntryPoint = "_WD_RegisterVideoPreviewCB#12", ExactSpelling = true)]
static extern int WD_RegisterVideoPreviewCB(IntPtr hChannel, object pContext, VideoCaptureCB_Ptr pCB);
Then I re-declare the C++ struct and CALLBACK in C# like this:
public delegate void VideoCaptureCB_Ptr(IntPtr pContext, byte[] apData, VideoSampleInfo_T pVSI);
[StructLayout(LayoutKind.Sequential)]
public struct VideoSampleInfo_T
{
public uint idFormat;
public uint lSignalState;
public int nLen; // not used for raw video data(e.g. YUV420)
public int nWidth;
public int nHeight;
public int[] anPitchs; // only used for raw video data(e.g. YUV420)
public uint dwMicrosecsPerFrame; // 1000*1000/FPS
public uint field;
public int iSerial;
}
And one delegate implement
public static void HandleVideoStatic(IntPtr pContext, byte[] apData, VideoSampleInfo_T pVSI)
{
}
When i run my code :
WD_RegisterVideoPreviewCB(m_ahChannels[i], m_aMediaHandler[i], HandleVideoStatic);
THe program show me an error does not match the unmanaged target signature.
I thinks encountered problem with the PVOID pContext, I changed it to object pContext. But I have to pass the m_aMediaHandler[i] (It's an instance of a class not a pointer) to it, the error raised " .."invalid agruments"
P/S: The WD_RegisterVideoPreviewCB call in C++
WD_RegisterVideoPreviewCB(m_ahChannels[i], &m_aMediaHandler[i], HandleVideoStatic);
i have a problem with convert a struct c++ to c# struct, i will leave the following code:
C++
struct SDK_ALARM_INPUTCONFIG
{
bool bEnable;
int iSensorType;
SDK_EventHandler hEvent;
};
struct SDK_EventHandler
{
unsigned int dwRecord;
int iRecordLatch;
unsigned int dwTour;
unsigned int dwSnapShot;
unsigned int dwAlarmOut;
unsigned int dwMatrix;
int iEventLatch;
int iAOLatch;
SDK_PtzLinkConfig PtzLink[NET_MAX_CHANNUM];
SDK_CONFIG_WORKSHEET schedule;
bool bRecordEn;
bool bTourEn;
bool bSnapEn;
bool bAlarmOutEn;
bool bPtzEn;
bool bTip;
bool bMail;
bool bMessage;
bool bBeep;
bool bVoice;
bool bFTP;
bool bMatrixEn;
bool bLog;
bool bMessagetoNet;
bool bShowInfo;
unsigned int dwShowInfoMask;
char pAlarmInfo[8];
bool bShortMsg;
bool bMultimediaMsg;
};
struct SDK_PtzLinkConfig
{
int iType;
int iValue;
};
struct SDK_CONFIG_WORKSHEET
{
SDK_TIMESECTION tsSchedule[6][7];
};
struct SDK_TIMESECTION
{
int enable;
int startHour;
int startMinute;
int startSecond;
int endHour;
int endMinute;
int endSecond;
};
C#:
[StructLayout(LayoutKind.Sequential)]
public struct SDK_ALARM_INPUTCONFIG
{
public bool bEnable;
public int iSensorType;
public SDK_EventHandler hEvent;
};
[StructLayout(LayoutKind.Sequential)]
public struct SDK_EventHandler
{
public ushort dwRecord;
public int iRecordLatch;
public ushort dwTour;
public ushort dwSnapShot;
public ushort dwAlarmOut;
public ushort dwMatrix;
public int iEventLatch;
public int iAOLatch;
[MarshalAs(UnmanagedType.ByValArray, ArraySubType=UnmanagedType.Struct, SizeConst = 32)]
public SDK_PtzLinkConfig[] PtzLink;
public SDK_CONFIG_WORKSHEET schedule;
public bool bRecordEn;
public bool bTourEn;
public bool bSnapEn;
public bool bAlarmOutEn;
public bool bPtzEn;
public bool bTip;
public bool bMail;
public bool bMessage;
public bool bBeep;
public bool bVoice;
public bool bFTP;
public bool bMatrixEn;
public bool bLog;
public bool bMessagetoNet;
public bool bShowInfo;
public ushort dwShowInfoMask;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 64)]
public string pAlarmInfo;
//public bool bShortMsg;
//public bool bMultimediaMsg;
};
[StructLayout(LayoutKind.Sequential)]
public struct SDK_PtzLinkConfig
{
public int iType;
public int iValue;
};
[StructLayout(LayoutKind.Sequential)]
public struct SDK_CONFIG_WORKSHEET
{
[MarshalAs(UnmanagedType.ByValArray, ArraySubType=UnmanagedType.Struct, SizeConst = 6*7)]
public SDK_TIMESECTION[] tsSchedule;
};
[StructLayout(LayoutKind.Sequential)]
struct SDK_TIMESECTION
{
public int enable;
public int startHour;
public int startMinute;
public int startSecond;
public int endHour;
public int endMinute;
public int endSecond;
};
I'm calling this method:
C++:
long H264_DVR_GetDevConfig(long lLoginID, unsigned long dwCommand, int nChannelNO, char * lpOutBuffer, unsigned long dwOutBufferSize, unsigned long* lpBytesReturned,int waittime = 1000);
C#:
[DllImport("NetSdk.dll")]
public static extern int H264_DVR_GetDevConfig(int lLoginID, uint dwCommand, int nChannelNO, IntPtr lpOutBuffer,
uint dwOutBufferSize, ref uint lpBytesReturned, int waittime);
I'm calling this way:
C#:
var vAlarmConfig = new SDK_ALARM_INPUTCONFIG();
IntPtr ptr = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(SDK_ALARM_INPUTCONFIG)));
Marshal.StructureToPtr(vAlarmConfig, ptr, true);
uint lpBytesReturned = (uint)Marshal.SizeOf(typeof(SDK_ALARM_INPUTCONFIG));
int CHANNEL = 2;
int result = XMSDK.H264_DVR_GetDevConfig(lLoginID, (uint)SDK_CONFIG_TYPE.E_SDK_CONFIG_ALARM_IN, CHANNEL, ptr,
(uint)Marshal.SizeOf(typeof(SDK_ALARM_INPUTCONFIG)), ref lpBytesReturned, 10000);
Seems everything work fine, but when i run the program, the method return an illegal paramater.
What i'm doing wrong?. I think the problem is the conversion.
Regards.
Your C++ bool is a single byte. But the C# bool default marshaling is as the 4 byte Winapi BOOL type. You'll need to add [MarshalAs(UnmanagedType.U1)] for every bool in your structs.
Your use of ushort is wrong. On the C++ side you have unsigned int. That is uint on the C# side.
You will also need to translate the structs accurately. Perhaps while you were debugging you made pAlarmInfo have length 64 rather than 8. Obviously you need to go back an do that correctly.
I guess you made that change because the struct size was incorrect. That should have been a tell-tale sign that there was a more serious problem. Your structs have to line up for each and every member. You can't just add a load of padding at the end to get the size right. If the sizes don't match then the layout will be wrong. You make the sizes match as a consequence of making the layouts match. When the latter is done correctly, the former happens as a consequence.
I have three C++ structures that I need to send as parameters when calling a DLL method from C#.
I simplified them as the following:
typedef struct
{
int data1;
int data2;
} A;
typedef struct
{
int numStructA;
A *pStructA;
int moreData;
} B;
typedef struct
{
TCHAR *pStr;
B structB;
} C;
The following is the C++ function I need to call from C#:
int func(C *pStructC, int numStructC);
In my C# code, I define the structs as the following:
[StructLayout(LayoutKind.Sequential, Pack = 1)]
private struct A
{
public int data1;
public int data2;
}
[StructLayout(LayoutKind.Sequential, Pack = 1)]
private struct B
{
public int numStuctA;
public IntPtr structA;
public int moreData;
}
[StructLayout(LayoutKind.Sequential, Pack = 1)]
private struct C
{
[MarshalAs(UnmanagedType.LPTStr)]
public string Str;
[MarshalAs(UnmanagedType.Struct)]
public B structB;
}
[DllImport("somedll.dll")]
private static extern int func(IntPtr pStructC, int size);
I tried to marshal the nested structures. However, the C++ function does not receive the data correctly. So far only the data that comes before the nested structure is sent correctly to the C++ function.
How can I marshal the nested structures so the C++ method receives the correct data? Thanks in advance.